Bile

The consumed food gets digested with the help of several glands and these glands are called digestive glands. These glands produce various types of juices for the breaking down of food into smaller particles, and they are salivary glands present in the mouth, gastric glands present in the stomach, the pancreas, and the liver. In this article let us learn about what is bile? Where is bile produced and stored? How does it play the main role in the process of digestion? 

What is Bile?

Bile is derived from the Latin word “Bilis” which is maybe a dark-green to yellowish-brown fluid produced by the liver of most vertebrates that helps in the digestion of lipids within the intestine. In humans, bile is secreted from the liver continuously and is stored and concentrated within the gallbladder. After the consumption of food, this stored bile is discharged into the duodenum to perform the process of digestion.

Bile Contents

The composition of hepatic bile is as follows, 

97–98% of water

0.7% bile salts

0.2% bilirubin

0.51% fats such as cholesterol, fatty acids, and lecithin

200 meq/l of inorganic salts

The two main pigments of bile are bilirubin, which is orange-yellow, and its oxidized form is biliverdin, which is green in color. When these two pigments are mixed, they are liable for the brown color of feces. About 400 to 800 milliliters of bile is produced per day in the adult citizenry.

Role of Bile in the Process of Digestion

The liver secretes bile or gall that acts as a surfactant to some extent, that helps to emulsify the lipids in food. Bile salt consists of anions that are hydrophilic on one side and hydrophobic on the other side. Consequently, they have a tendency to aggregate around droplets of lipids such as triglycerides and phospholipids to make micelles. In the micelles, the hydrophobic sides are faced inwards to the fat, and the hydrophilic sides facing outwards. The hydrophilic sides of the micelles are charged and these charged micelles sides are required to prevent the fat droplets from re-aggregating into larger fat particles that are coated with bile. In the case of humans, the micelles that are present in the duodenum have a diameter of around 1–50 μm.

The dispersion of food fat into micelles provides a greatly increased area for the action of the enzyme pancreatic lipase, which actually digests the triglycerides, and is in a position to reach the fatty core through gaps that are present in between the bile salts. A triglyceride is formed into two fatty acids and a monoglyceride is absorbed by the villi that are present on the walls of the intestine. After being transferred across the intestinal membrane, the fatty acids reform into triglycerides by the process called re-esterification, before being absorbed into the systema lymphatica through lacteals. In the absence of bile salts, most of the lipids that are obtained from food would be undigested and excreted in feces.

The liver, the place where is bile released, increases the absorption of fats, it's a crucial part of the absorption of fat-soluble substances, like vitamins A, D, E, and K. A byproduct of red blood cells that are recycled by the liver produces bilirubin, along with the digestive function it acts as a route for excretion of the bilirubin. Bilirubin derives from hemoglobin by glucuronidation.

Microscopic View of Bile

Use of Bile in Human Body

• Aid digestion by breaking down fats, 

• allowing fat-soluble vitamins to be absorbed 

• waste products to be eliminated

• Laxative Action by inducing peristalsis

• Cholagogue Action by acting as a stimulant in and of itself

• Bile Helps to Maintain a Suitable pH

• Bile mucin acts as a lubricant and a buffer.

• Regurgitation of bile in the stomach aids in the neutralisation of gastric acidity, preventing acid damage to the gastric mucosa.

More to Know

• Bile tends to be alkaline on average. 

• The pH of bile juice is 7.50 to 8.05 which is said to be more than that of the corresponding gallbladder bile acid pH is 6.80 to 7.65. 

• Bile within the gallbladder becomes more acidic the longer an individual goes without eating, though resting slows this fall in pH. 

• As an alkali, it also has the function of neutralizing excess stomach acid before it enters the duodenum, the primary section of the tiny intestine. 

• Bile salts also act as bactericides, destroying many of the microbes which will be present within the food.

Conclusion

The fluid that is made and released by the liver is considered bile. The main and important function of the bile is to help in the digestion of fats into fatty acids. In the absence of bile, the consumed fats or the vitamins that are required to dissolve the fat get accumulated in the colon of the intestine where it causes several complications.